1. Field of the Invention
The present invention relates to a curable composition to be used for a printed wiring board, in particular a UV curable composition for use in inkjet printing method, a cured coating film to be used for a printed wiring board as a resist, or for marking or etching, and a printed wiring board comprising the cured film having a predetermined pattern.
2. Discussion of the Related Art
For the production of a flexible printed wiring board or a tape carrier package, the following types of resists are used:
(1) A resist obtained by stamping a polyimide film, i.e., so-called cover lay film, with a mold in the shape corresponding to a resist pattern to be obtained, adhering the stamped film to a substrate by using an adhesive agent, and curing the film, as disclosed JP-B (Kokoku) 5 (1993)-75032;(2) A resist obtained by applying a photocurable composition to a substrate by screen printing to form a flexible film, and curing the film, as disclosed in JP-A 10 (1998)-224018;(3) A resist obtained by applying a photocurable and thermosetting resin composition to a substrate, and exposing the composition to light, developing and curing the same, as disclosed in JP-A 9 (1997)-54434.
Among these, photocurable composition (2) is preferably used, which is prepared with small number of pattern forming steps and short tact time, especially because of fast setting.
It is necessary, for the above-mentioned curable compositions, to secure adhesion with respect to both plastic substrate based on polyimide or the like and a metal for a conductive circuit provided on the substrate. In addition to the above, the curable compositions have to have many necessary properties such as resistant to soldering. The film obtained from photocurable composition disclosed in JP-A 10 (1998)-224018, however, has insufficient flexibility. Therefore, it is difficult to obtain an excellent adhesion with respect to both a plastic substrate and metal as a conductive circuit, and hence a further improvement is desired.